In many recipes for cakes and baking the advice is to cream butter and sugar before adding other ingredients. Softening the butter makes the process easier, but how soft can the butter be? If the butter is melted would it make any difference to the outcome of the recipe - or should one just stick to what the recipe states?

- Russell Finnemore

Cake baking is one branch of cooking that you truly do need to follow the instructions carefully - because if you don't you may end up with something resembling a tin of damp porridge or dry cement rather than a light and fluffy sponge cake. So, please do stick to what the recipe states. Once you've mastered the art of the recipe, and in many ways it is an art, then you can with confidence begin to tweak and adjust a little here and there.

The reason melted butter and softened butter behave differently is that you can beat an awful lot of air into softened butter that you can't into melted butter. Softened butter is simply butter at room temperature (think of a room in late spring, not in a snow-covered winter). Imagine putting a block of softened butter and a cup of sugar into a food mixer and beating it - you'll end up with something resembling golden meringue.

Do the same with a block of melted butter and it resembles yellow whipped fat. Melting butter, then cooling it and trying to whip it again never gives the same good result that softened butter gives, so make sure if you soften your butter in a microwave, or on top of the stove that you don't melt it too much. Slowly and gently is the key to success.

Beating a lot of air into the "batter" allows the mixture to rise up when baked, as the tiny air bubbles in the batter expand with heat and cause the mixture to grow in size. As the heat increases, the eggs in the batter (if it contains them) begin to set and therefore the mixture doesn't collapse once it cools. The combination of fat and flour also sets the batter (if used in the correct proportion) and again this prevents the mixture from collapsing once it cools.

For this same reason, it's impossible to substitute oils for softened butter in many recipes. Oils can be used successfully in some cakes and muffins, as explained in this column some weeks back now, but it will be impossible to get a light fluffy cake from an oil-based batter. Oils are best used in dense cakes like carrot cake as their purpose is to provide moisture to the cake which means it will keep well without drying out too much.

Another area where the butter's consistency is important is in the making of pastry. There are myriad recipes out there. In some butter is rubbed into the dry ingredients and in others, admittedly fewer, it's melted and stirred in. In puff pastry butter is used in two different ways. The first amount of butter, icy cold, is rubbed into the dry ingredients and used to form a dough. Then a second amount of butter, slightly cooler than at room temperature, is formed into a book-shaped block which is wrapped in the dough. It's rolled out and folded into three, again and again with resting in between. What this means is that eventually, once the process is finished, you have many layers of very thin dough separated by very thin layers of butter. When the pastry is baked the layers of butter expand but are kept separate by the dough - which causes the pastry to rise. The French created a puff pastry dessert called millefeuille (found in many good cake shops) which translates to "a thousand leaves" (or sheets) which is very apt.

So, to reiterate, if the recipe says softened butter then it needs to be of the consistency of margarine rather than oil. It needs to have body and be "spreadable" with a knife. If you think it's a little too soft, place in the fridge for 10 minutes or so to firm it up a little. But first and foremost, make sure you follow the instructions to the dot because they've been written for a reason.